Polyamides (PA)

What are polyamides (PA)?

Polyamides are semi-crystalline thermoplastics with a crystallinity of up to 60%. They are produced by polycondensation of an amino and a carboxylic acid group; aminocarboxylic acids containing both groups are often used directly as monomers. Polyamide is an umbrella term and there are many different types, depending on the monomer used. The types are usually labeled with PA and a number, whereby the number corresponds to the number of carbon atoms in the monomers. PA 6 is produced from a single monomer, caprolactam, with a 6-carbon chain. PA 6.6, on the other hand, consists of two monomers (hexamethylenediamine and adipic acid) with 6 carbons each. The most important types are standardized in DIN EN ISO 1043-1.

All polyamides have a high water absorption (up to 3.5 %), which also ensures very good impact strength, rigidity, abrasion resistance and sliding properties. Due to the combination of good water absorption and good damping capacity, PAs are often used in damping technology. Polyamides are generally resistant to solvents, hydrocarbons, oils, gasoline and greases. They are susceptible to acids, strong alkalis and oxidizing agents. With the exception of impact strength, most properties can be improved by glass fiber reinforcement.

PA 66 has even better hardness and heat resistance, making it particularly suitable for use at high temperatures. In general, the upper continuous operating temperature is 80 – 150 °C, depending on the material.

PA 610/612/11 and 12 have a slightly lower water absorption and therefore a lower hardness.

PA 6-3-T is one of the few amorphous polyamides which allows the listed properties to be combined with transparency, but at the same time increases susceptibility to stress cracking.

PA6, PA6.6 and PA12 are also available in glass fiber reinforced (PA GF), which improves some mechanical properties.

Polyamides are used in mechanical engineering, vehicle construction, electrical engineering and sanitary engineering.